PROJECT SUMMARY On a daily basis we are challenged with the task of evaluating and predicting the behaviors of others. Other minds are complex and inherently variable, evolved to outwit simple predictions made by predators, prey, or rivals. One way that the brain could limit the scope of this challenge is by learning sets of probable behaviors that another individual may engage in, and forming behavioral strategies that fit these ?expectation sets.? The idea that the brain links sets of expectations with behavioral strategies fits well with proposed functions of the rostral cingulate cortex (or medial prefrontal cortex, mPFC). The mPFC has been shown to be necessary for a number of social behaviors, and dysfunction of this region has been proposed to contribute to symptoms of Autism Spectrum Disorders (ASD) and social deficits in other mental health conditions. It is hypothesized that social cognition depends on the mPFC due to its ability to learn expectation sets and/or associate these with a strategy (or ?schema?) for interacting with specific individuals. The goals of this research are to test two predictions of this hypothesis: first, that rodent dyads develop specific patterns of interactions as the animals gain experience with on-another (Aim 1) and, second, that neuron population activity in the mPFC discriminates more strongly between familiar compared with novel conspecifics (Aim 2). The experiments of this project will investigate social learning by applying ?computational ethology? and electrophysiological recording methods to studying the brain and behavior of degus, a highly social species of rodent. Computational ethology refers to the use of computational tools to draw inferences about animal behavior based on highly multivariate, behavioral observation data. This method is well suited for studies of social cognition, where restricting behaviors for the sake of experimental control can impact the extent to which an animal relies on high-level sets of expectations and strategies. Multi- single-neuron electrophysiological recordings will provide evidence of whether or not the mPFC differentiates between individuals associated with different expectation sets and/or interaction strategies. Finally, the purpose of using degus is to take advantage of their frequent, highly expressive, and easily-measurable physical and vocal interactions, along with existing evidence that dyads exhibit distinct interaction patterns. Behavior and neural activity will be monitored while adult, same-sex degus are united in multiple social exposure sessions, and analyses will primarily address how patterns differ and change over time in stranger compared with familiar dyads. The project will add to our knowledge on social cognition and provide a methodological foundation for future investigations, initiating a long-term research program on how social expectations are formed and how this may be disrupted. These experiments will also create many student training opportunities in systems and behavioral neuroscience, in part by creating a rich database available for a wide spectrum of independent student projects.